In this patent there is disclosed a process for the production of padding in synthetic or other fibres, the improvement comprising the steps of:
first producing a web including a layer obtained by carding a mixture of fibres of polyester or other fibres with silicone treated fibres of diverse nature and origin;
treating one side of said web with a mixture of bonding agents of stickly plastic consistency which, when polymerised, create a very soft and elastic film;
spray-applying on the opposite side of said web from said one side thereof another type of bonding agent, of different nature, which is not sticky;
passing said web, thus treated, through a calender composed of two or more cylinders; and
heating said cylinders whereby to cause said sticky plastic bonding agent to adhere to the facing roller in the region of separation of said web from said rollers such that said layer of fibres is caused partially to separate to create air spaces therein.
By suitably regulating the pressure and the temperature of the cylinders, a desired and adjustable reduction of thickness can be obtained, and, simultaneously, the effect of the adhesion of the plastic side of the adhesive layer as the layer is being separated from the cylinder, there takes place a slight reinflation which creates an "air chamber" or air pocket within the layer.
An advantage of this process is that the formation of the air chamber or air pocket is also favoured by the presence of the silicone treated and therefore slippery fibres. This process makes it possible to reduce the desired thickness paddings having very high weight per square meter, which constitutes a considerable advantage as far as use of the padding for garments is concerned.
Another advantage is represented by the possibility of obtaining by means of the calendering operation, more or less any thickness of finished padding from a single given material starting thickness by appropriately varying the temperature and pressure of the cylinder.
In particular this process for the production of padding can be performed on webs of layers comprising a mixture of polyester or other fibres with silicone treated fibers of different nature and origin.
This mixture of fibers, by means of carding machines, is formed into a layer, which is resin bonded with a mixture of adhesives for the purpose of making it more compact and for fixing the nap.
More specifically, there are used two mixtures of adhesives: a first sticky plastic adhesive which, when polymerised, creates a very soft and elastic film on one side of the padding; on the other side, there is sprayed another type of adhesive, of different nature, which is not sticky.
The product which results from this has a soft and voluminous aspect; however, for the requirements of fashion or for other requirements, there exists the necessity of having the product in layers of high weight per square meter, and therefore of high insulating property, but reduced thickness. To achieve this the layer of padding, produced as described above, is made to pass through a calender, composed of two or more cylinders heated to a chosen temperature. In particular, one of the cylinders or of each pair of cylinders if there is more than one pair (the lower cylinder as viewed in the drawings) is completely smooth and made of metal, whilst the other is clad with a material of a different nature, which is not smooth.
By suitably adjusting the pressure and the temperature and arranging that the sticky plastic side of the layer faces towards the coated cylinder, the desired reduction in the thickness is obtained, and simultaneously, by the effect of the adhesion of the sticky plastic side of the layer itself to the cylinder in the region of separation from the cylinder, there occurs a slight reinflation which creates an "air chamber" or air pocket.
Alternatively, of course, the said calender could be constituted by entirely metal cylinders, or other non-clad materials. The presence of a layer, however thin, of adhesive, on one face of the layer, makes this latter adhere, at least over a certain section, to the facing cylinder. In practice, the expansion of the compressed material caused by this adhesion is controllable, and serves to create, in the material itself, zones of discontinuity, which reduce its specific weight and increase its thermal resistance. Thus it can be seen that the product thus obtained is able to offer a high thermal resistance without by this presenting excessive thickness.
The following table summarized, by way of example, the different insulation properties of three products, all produced starting from layers of superimposed cohered fibres of polyester, and all having the same weight per unit of surface area but of course all having different thicknesses, the thinnest being the product according to the invention of said granted U.S. Pat. No. 4,551,383.
______________________________________ Traditional Stitched Production of the Product Wadding Wadding invention ______________________________________ Thickness 0,6 mm 0,6 mm 0,6 mm Weight in 30 50 120 grammes Insulation 100 130 290 Traditional wadding + 100 ______________________________________
This above-described padding has thermal insulating characteristic which are a significant improvement over those encountered in paddings of known type which, among other things, are generally rather thick and therefore do not lend themselves well to application in the field of clothing; moreover, such known padding materials do not have such good thermal insulation characteristics as can be achieved with the padding material of the applicant's earlier patent application referred to above.